JP2013199579A - Acrylic adhesive, adhesive for optical member, optical member with adhesive layer using the same, image display device, method of producing acrylic adhesive, and acrylic adhesive composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acrylic adhesive that is to obtain an adhesive for an optical member that excels in durability (especially, durability under a severe moist heat condition), and that excels in optical characteristics of light leakage resistance and transparency or the like, and reworkability.SOLUTION: An acrylic adhesive is characterized in that an acrylic resin (A) is crosslinked by a reaction product of a polyfunctional isocyanate compound (B) and a multifunctional thiol (C).

Description

  The present invention relates to an acrylic pressure-sensitive adhesive, and more specifically, an acrylic pressure-sensitive adhesive exhibiting excellent durability, light leakage resistance, reworkability, and transparency when used as a pressure-sensitive adhesive for optical members, and The present invention relates to an optical member with an adhesive layer and an image display device using the same, and further relates to a method for producing such an acrylic adhesive.

  Conventionally, a polarizing plate that is obtained by coating both surfaces of a polyvinyl alcohol film or the like (polarizer) imparted with polarizing properties with a cellulose triacetate film or the like has a liquid crystal component aligned between two glass plates sandwiched therebetween. The liquid crystal cell is laminated on the glass surface to form a liquid crystal display panel, and an adhesive is used for laminating the polarizing plate and the liquid crystal cell.

  Furthermore, in order to improve the display quality, the liquid crystal cell is laminated with optical members other than the polarizing plate (an optical film such as a phase difference plate, an optical compensation film, a brightness enhancement film, and a viewing angle widening film). An adhesive is also used for bonding these optical members.

  In general, it is known that a dimensional change occurs in an optical film of an optical member to be formed due to a use environment of a liquid crystal display, heat generated during long-term operation, or the like. For example, a polarizing plate has a multi-layered structure of dissimilar materials and has poor dimensional stability due to the characteristics of the constituent materials. In particular, under a high-temperature, high-humidity heat environment, the dimensional change due to shrinkage and expansion is large and stress is concentrated. Color unevenness and light leakage occur in the portion, and the problem of deterioration in display quality occurs. Furthermore, when the liquid crystal display is used in a high-temperature and high-humidity heat environment, there is a problem that problems such as foaming and peeling are likely to occur at the interface between the pressure-sensitive adhesive and the glass substrate.

  In recent years, in the use of an adhesive for optical members, when it is bonded to a substrate such as glass, it may be necessary to re-stick due to a bonding error or the like. It is also required to be excellent.

  In order to solve such problems, various adhesives for optical members having improved durability and optical properties (light leakage resistance, transparency) and reworkability have been developed. It is a pressure-sensitive adhesive obtained by blending a larger amount of isocyanate cross-linking agent than usual with respect to an acrylic resin containing a group and a hydroxyl group as essential components, and the content ratio of carboxyl group, hydroxyl group and isocyanate group is adjusted to a specific ratio. A pressure-sensitive adhesive for optical films comprising a pressure-sensitive adhesive composition has been proposed.

JP2011-85887A

  However, in the technique disclosed in Patent Document 1, the reaction between isocyanate-based cross-linking agents contained in a larger amount than usual does not easily proceed, and it is difficult to obtain a pressure-sensitive adhesive having a strong network structure. In addition, durability, light leakage resistance, and reworkability under high temperature and high humidity conditions are not sufficient, and the amount of the three types of functional groups must be adjusted, making it difficult to adjust the balance of physical properties and sticking stably. It is difficult to produce an agent, and when a large amount of an isocyanate-based crosslinking agent is contained, there is a problem that it takes time until the crosslinking reaction is completed.

  Therefore, in the present invention, for such an optical member that has excellent durability (particularly durability under severe wet heat conditions) and excellent optical characteristics such as light leakage resistance and transparency and reworkability in such a background. The object is to provide an acrylic pressure-sensitive adhesive for obtaining the pressure-sensitive adhesive.

  However, as a result of intensive studies in view of such circumstances, the present inventors have found that an acrylic pressure-sensitive adhesive obtained by using an acrylic resin and an isocyanate-based cross-linking agent is further increased in addition to the acrylic resin and the isocyanate-based cross-linking agent. When a functional thiol is blended, an isocyanate-based cross-linking agent and a polyfunctional thiol react, and the reaction product and the acrylic resin cross-link, resulting in an acrylic pressure-sensitive adhesive having a good balance in durability, optical properties, and reworkability. As a result, the present invention has been completed.

That is, the gist of the present invention is an acrylic pressure-sensitive adhesive characterized in that the acrylic resin (A) is crosslinked with a reaction product of a polyfunctional isocyanate compound (B) and a polyfunctional thiol (C). is there.
Furthermore, this invention relates to the adhesive for optical members, the optical member with an adhesive layer using the same, an image display apparatus, the manufacturing method of an acrylic adhesive, and an acrylic adhesive composition.

The acrylic pressure-sensitive adhesive of the present invention is an optical member pressure-sensitive adhesive that has excellent durability (particularly durability under severe wet heat conditions) and excellent optical properties such as light leakage resistance and transparency and reworkability. It is the most suitable pressure-sensitive adhesive to obtain, in particular, the acrylic resin and the reaction product of isocyanate compound and thiol compound are highly compatible, so it is very transparent, and more crosslinking agent is used than usual. Nevertheless, it takes less time than usual until the crosslinking reaction is completed.
In addition, when the polyfunctional isocyanate compound (B) and the polyfunctional thiol (C) are reacted in the presence of the acrylic resin (A), the pressure-sensitive adhesive has an interpenetrating network structure (IPN) structure. Therefore, the elastic modulus of the pressure-sensitive adhesive increases, and the contraction of the polarizing plate is suppressed, resulting in end-concentrated light leakage. Furthermore, the IPN structure can be removed when force is applied slowly. Therefore, the pressure-sensitive adhesive has high stress relaxation properties. As a result, the stress of the acrylic pressure-sensitive adhesive layer and the optical film is relaxed, and light leakage is less likely to occur.

The present invention will be described in detail below, but these show examples of desirable embodiments.
In the present invention, (meth) acryl means acryl or methacryl, (meth) acryloyl means acryloyl or methacryloyl, and (meth) acrylate means acrylate or methacrylate.

The acrylic pressure-sensitive adhesive of the present invention is an acrylic pressure-sensitive adhesive obtained by crosslinking an acrylic resin (A) with a reaction product of a polyfunctional isocyanate compound (B) and a polyfunctional thiol (C).
First, the said (A)-(C) component which forms the acrylic adhesive of this invention is demonstrated.

  The acrylic resin (A) used in the present invention comprises a (meth) acrylic acid ester monomer (a1), a functional group-containing monomer (a2), an aromatic ring-containing monomer (a3), and other copolymerizable monomers (a4). Polymerization component [I] containing a monomer selected from is homopolymerized or copolymerized.

  Examples of the (meth) acrylic acid ester monomer (a1) include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, iso-butyl (meth) acrylate, tert-butyl (meta ) Acrylate, n-propyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, iso-octyl (meth) acrylate, isodecyl (meth) acrylate, lauryl (Meth) acrylate alkyl ester such as (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate, iso-stearyl (meth) acrylate; cyclohexyl (meth) acrylate, isobornyl (meth) Cycloaliphatic (meth) acrylic acid esters such as acrylate and the like. In the case of the above (meth) acrylic acid alkyl ester, the alkyl group preferably has 1 to 20 carbon atoms, particularly preferably 1 to 12, more preferably 1 to 8, and particularly preferably 4 to 8. These can be used alone or in combination of two or more.

  Among such (meth) acrylic acid alkyl ester monomers (a1), n-butyl (meth) acrylate and 2-ethylhexyl (meth) are preferable in terms of copolymerizability, adhesive properties, ease of handling, and availability of raw materials. An acrylate is preferably used, and more preferably n-butyl (meth) acrylate is used in terms of excellent durability.

  Examples of the functional group-containing monomer (a2) (excluding (a3) described later) include, for example, a hydroxyl group-containing monomer, an amino group-containing monomer, an acetoacetyl group-containing monomer, an isocyanate group-containing monomer, a carboxyl group-containing monomer, and a glycidyl group. Examples of such a monomer include a carboxyl group-containing monomer because of its excellent adhesion.

  Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 5-hydroxypentyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl ( Hydroxyalkyl esters of acrylic acid such as (meth) acrylate, caprolactone-modified monomers such as caprolactone-modified 2-hydroxyethyl (meth) acrylate, oxyalkylene-modified monomers such as diethylene glycol (meth) acrylate and polyethylene glycol (meth) acrylate, 2- Primary hydroxyl group-containing monomers such as acryloyloxyethyl 2-hydroxyethylphthalic acid and N-methylol (meth) acrylamide; 2-hydroxypropyl (meth) acrylic acid Rate, secondary hydroxyl group-containing monomers such as 2-hydroxybutyl (meth) acrylate; can be mentioned 2,2-dimethyl 2-hydroxyethyl (meth) tertiary hydroxyl group-containing monomers acrylate. These can be used alone or in combination of two or more.

  Among the above hydroxyl group-containing monomers, it is preferable to use those having a content of di (meth) acrylate as an impurity of 0.5% or less, particularly preferably 0.2% or less, and more preferably 0.1% or less. Are preferably used. Specifically, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and 4-hydroxybutyl acrylate are preferable, and 2-hydroxyethyl acrylate, 2-hydroxybutyl acrylate are particularly preferable in terms of copolymerizability, adhesive physical properties, ease of handling, and availability of raw materials. Hydroxyethyl acrylate.

  Examples of the carboxyl group-containing monomer include (meth) acrylic acid, acrylic acid dimer, crotonic acid, maleic acid, maleic anhydride, fumaric acid, citraconic acid, glutaconic acid, itaconic acid, acrylamide N-glycolic acid, and cinnamon. An acid etc. are mentioned, Especially, (meth) acrylic acid is used preferably.

  Examples of the amino group-containing monomer include t-butylaminoethyl (meth) acrylate, ethylaminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, and the like.

  Examples of the acetoacetyl group-containing monomer include 2- (acetoacetoxy) ethyl (meth) acrylate and allyl acetoacetate.

  Examples of the isocyanate group-containing monomer include 2-acryloyloxyethyl isocyanate, 2-methacryloyloxyethyl isocyanate, and alkylene oxide adducts thereof.

Examples of the glycidyl group-containing monomer include glycidyl (meth) acrylate and allyl glycidyl (meth) acrylate.
These functional group-containing monomers (a2) may be used alone or in combination of two or more.

Examples of the aromatic ring-containing monomer (a3) include phenyl (meth) acrylate, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, ethoxylated o-phenyl (meth) acrylate, phenyldiethylene glycol (meth) acrylate, and 2-hydroxy Examples include -3-phenoxypropyl (meth) acrylate, 3-chloro-2-hydroxypropyl (meth) acrylate, styrene, and α-methylstyrene.
The aromatic ring-containing monomer (a3) is preferably used for adjusting the birefringence of the pressure-sensitive adhesive layer. By adjusting the content of the aromatic ring-containing monomer, a film such as a polarizing plate contracts. By preventing the occurrence of birefringence in the pressure-sensitive adhesive or adjusting the birefringence of the pressure-sensitive adhesive, the resulting light leakage can be further suppressed.

  Other copolymerizable monomers (a4) include, for example, (2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, 3-methoxybutyl (meth) acrylate, 2-butoxyethyl (meth) acrylate 2-butoxydiethylene glycol (meth) acrylate, methoxydiethylene glycol (meth) acrylate, methoxytriethylene glycol (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, methoxydipropylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, Octoxy polyethylene glycol-polypropylene glycol-mono (meth) acrylate, lauroxy polyethylene glycol mono (meth) acrylate, Ether chain-containing (meth) acrylic acid ester monomers such as alloxypolyethylene glycol mono (meth) acrylate; acrylonitrile, methacrylonitrile, vinyl acetate, vinyl propionate, vinyl stearate, vinyl chloride, vinylidene chloride, alkyl vinyl ether, vinyl toluene, Vinylpyridine, vinylpyrrolidone, itaconic acid dialkyl ester, fumaric acid dialkyl ester, allyl alcohol, acrylic chloride, methyl vinyl ketone, N-acrylamidomethyltrimethylammonium chloride, allyltrimethylammonium chloride, dimethylallyl vinylketone, (meth) acryloylmorpholine, etc. These may be used alone or in combination of two or more.

The content ratio of the (meth) acrylic acid ester monomer (a1) is usually 50 to 100% by weight, preferably 75 to 99% by weight, particularly preferably 80 to 97% by weight, based on the whole polymerization component [I]. More preferably, it is 90 to 95% by weight.
When there is too little content of this (meth) acrylic acid ester type monomer (a1), when it uses as an adhesive, it exists in the tendency for adhesive force to fall.

The content of the functional group-containing monomer (a2) is usually 0 to 50% by weight, preferably 1 to 25% by weight, particularly preferably 3 to 20% by weight, and more preferably based on the entire polymerization component [I]. 5 to 10% by weight.
When there are too many such functional group-containing monomers (a2), the viscosity tends to increase or the stability of the resin tends to decrease.

The content of the aromatic ring-containing monomer (a3) is preferably 1 to 80% by weight, particularly preferably 5 to 60% by weight, more preferably 10 to 50% by weight based on the entire polymerization component [I]. %, Particularly preferably 15 to 40% by weight.
When the amount of the aromatic ring-containing monomer (a3) is too large, the adhesive property tends to be lowered, and when the amount is too small, the light leakage resistance tends to be hardly exhibited.

The content of the other copolymerizable monomer (a4) is preferably 0 to 50% by weight, particularly preferably 0.5 to 20% by weight, more preferably 1 to 10%, based on the entire polymerization component [I]. % By weight.
When there is too much content of this other copolymerizable monomer (a4), it exists in the tendency for the effect of invention to become difficult to be acquired.

  In this invention, the monomer selected from the said (meth) acrylic acid ester monomer (a1), a functional group containing monomer (a2), an aromatic ring containing monomer (a3), and another copolymerizable monomer (a4) is contained. The acrylic resin (A) is produced by homopolymerizing or copolymerizing the polymerization component [I]. Such polymerization can be carried out by a conventionally known method such as solution radical polymerization, suspension polymerization, bulk polymerization, emulsion polymerization, etc., but the acrylic resin (A) can be safely and stably used in any monomer composition. Solution radical polymerization is preferred in that it can be produced.

  In such solution polymerization, for example, an (meth) acrylic acid alkyl ester monomer (a1), a functional group-containing monomer (a2), an aromatic ring-containing monomer (a3), and other copolymerizable monomers (a4) in an organic solvent. A monomer component such as the above and a polymerization initiator may be mixed or dropped, and polymerization may be performed in a reflux state or at 50 to 98 ° C. for 0.1 to 20 hours.

  Examples of the organic solvent used for the polymerization include aromatic hydrocarbons such as toluene and xylene, esters such as methyl acetate, ethyl acetate and butyl acetate, aliphatic alcohols such as n-propyl alcohol and isopropyl alcohol, acetone, Examples include ketones such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone.

Examples of the polymerization initiator used for such radical polymerization include 2,2′-azobisisobutyronitrile, 2,2′-azobis-2-methylbutyronitrile, which are ordinary radical polymerization initiators, Azo initiators such as 4,4′-azobis (4-cyanovaleric acid), 2,2′-azobis (methylpropionic acid), benzoyl peroxide, laurolyl peroxide, di-t-butyl peroxide, cumene Examples thereof include organic peroxides such as hydroperoxide, which can be appropriately selected according to the monomer used. These polymerization initiators may be used alone or in combination of two or more.

  The weight average molecular weight of the acrylic resin (A) is usually 10,000 to 5,000,000, preferably 200,000 to 2,500,000, particularly preferably 600,000 to 2,000,000, particularly preferably 1,000,000 to 1,800,000. . When the weight average molecular weight is too small, the durability performance tends to be lowered. When the weight average molecular weight is too large, a large amount of a diluent solvent is required, which tends to be undesirable in terms of coating property and cost.

The degree of dispersion (weight average molecular weight / number average molecular weight) of the acrylic resin (A) is usually 50 or less, preferably 20 or less, particularly preferably 15 or less, more preferably 10 or less, particularly preferably. Is 5 or less.
When the degree of dispersion is too high, the durability performance of the pressure-sensitive adhesive layer is lowered, and foaming or the like tends to occur. The lower limit of the dispersity is usually 1.1, preferably 1.5, and more preferably 2 from the viewpoint of production limit.

  Further, the glass transition temperature of the acrylic resin (A) is preferably −80 to −10 ° C., particularly −65 to −30 ° C., more preferably −55 to −45 ° C., and the glass transition temperature is too high. When the adhesive strength is too low, the heat resistance tends to decrease.

Ｔg：共重合体のガラス転移温度（Ｋ）
Ｔga：モノマーＡのホモポリマーのガラス転移温度（Ｋ） Ｗa：モノマーＡの重量分率
Ｔgb：モノマーＢのホモポリマーのガラス転移温度（Ｋ） Ｗb：モノマーＢの重量分率
Ｔgn：モノマーＮのホモポリマーのガラス転移温度（Ｋ） Ｗn：モノマーＮの重量分率
（Ｗa＋Ｗb＋・・・＋Ｗn＝１） In addition, said weight average molecular weight is a weight average molecular weight by standard polystyrene molecular weight conversion, and it is a column in high performance liquid chromatography (The Japan Waters company "Waters 2695 (main body)" and "Waters 2414 (detector)"). : Shodex GPC KF-806L (exclusion limit molecular weight: 2 × 10 ⁷ , separation range: 100 to 2 × 10 ⁷ , theoretical plate number: 10,000 plates / piece, filler material: styrene-divinylbenzene copolymer, filler The particle diameter is measured by using three series of 10 μm), and the same method can be used for the number average molecular weight. The degree of dispersion is determined from the weight average molecular weight and the number average molecular weight. The glass transition temperature is calculated from the following Fox equation.

Tg: Glass transition temperature of copolymer (K)
Tga: Glass transition temperature of monomer A homopolymer (K) Wa: Weight fraction of monomer A Tgb: Glass transition temperature of homopolymer of monomer B (K) Wb: Weight fraction of monomer B Tgn: Homogeneity of monomer N Glass transition temperature of polymer (K) Wn: weight fraction of monomer N (Wa + Wb +... + Wn = 1)

The said polyfunctional isocyanate type compound (B) should just be a compound containing 2 or more isocyanate groups, and what is normally used as an isocyanate type crosslinking agent should just be used.
The number of such isocyanate groups is usually 2 to 10, preferably 2 to 5, and particularly preferably 2.5 to 3.5.

Examples of the polyfunctional isocyanate compound (B) include:
Tolylene diisocyanate compounds such as 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, xylylene diisocyanate compounds such as 1,3-xylylene diisocyanate, diphenylmethane diisocyanate compounds such as diphenylmethane-4,4-diisocyanate Compounds, aromatic polyfunctional isocyanate compounds such as naphthalene diisocyanate compounds such as 1,5-naphthalene diisocyanate;
Alicyclic rings such as isophorone diisocyanate, 1,4-cyclohexane diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, methylcyclohexane diisocyanate, isopropylidene dicyclohexyl-4,4′-diisocyanate, 1,3-diisocyanatomethylcyclohexane, norbornane diisocyanate Group polyfunctional isocyanate compounds;
Aliphatic polyfunctional isocyanate compounds such as hexamethylene diisocyanate and trimethylhexamethylene diisocyanate;
And adducts, burettes, and isocyanurates of the above polyfunctional isocyanate compounds. These may be used alone or in combination of two or more.

  Among these, aromatic polyfunctional isocyanate compounds are preferable, tolylene diisocyanate compounds are particularly preferable in terms of easy adjustment of the refractive index of the pressure-sensitive adhesive layer, more preferably an adduct of tolylene diisocyanate compounds, Particularly preferred is a trimethylolpropane adduct of a tolylene diisocyanate compound.

  The polyfunctional thiol (C) may be a compound containing two or more thiol groups, and the content of thiol groups is usually 2 to 10, preferably 2 to 6, particularly preferably 3 to 4. It is a piece.

Examples of the polyfunctional thiol (C) include:
Bifunctional thiols such as tetraethylene glycol bis (3-mercaptopropionate);
Trimethylolpropane tris (3-mercaptopropionate), tris-[(3-mercaptopropionyloxy) -ethyl] -isocyanurate, pentaerythritol tetrakis (3-mercaptopropionate), dipentaerythritol hexakis (3- And trifunctional or higher functional thiols such as mercaptopyropionate).
These may be used alone or in combination of two or more.

  Among these, trifunctional or higher functional thiols are preferable, and trimethylolpropane tris (3-mercaptopropionate), tris-[(3- Mercaptopropionyloxy) -ethyl] -isocyanurate, pentaerythritol tetrakis (3-mercaptopropionate), more preferably trimethylolpropane tris (3-mercaptopropionate).

  The acrylic pressure-sensitive adhesive of the present invention uses the above components (A) to (C), and the acrylic resin (A) is crosslinked with a reaction product of the polyfunctional isocyanate compound (B) and the polyfunctional thiol (C). Acrylic adhesive.

  In reacting the polyfunctional isocyanate compound (B) with the polyfunctional thiol (C), the blending ratio (weight ratio) of the polyfunctional isocyanate compound (B) and the polyfunctional thiol (C) is preferably (B). : (C) = 90: 10-20: 80, particularly preferably (B) :( C) = 80: 20-50: 50, more preferably (B) :( C) = 70: 30-60: 40 The blending ratio (molar ratio) of the isocyanate group contained in the polyfunctional isocyanate compound (B) and the mercapto group contained in the polyfunctional thiol (C) is preferably isocyanate group: mercapto group = 70: 30-30: 70, particularly preferably isocyanate group: mercapto group = 60: 40-40: 60, more preferably isocyanate group: mercapto group = 55: 45-4 : A 55, but it is preferred that both are used in equimolar about.

  If the amount of the polyfunctional thiol (C) is too large relative to the polyfunctional isocyanate compound (B), the mercapto group (thiol group) tends to remain and the aging period until the physical properties become stable tends to be long. Conversely, isocyanate groups tend to remain and the aging period until the physical properties are stable tends to be long.

The blending amount of the polyfunctional isocyanate compound (B) is preferably 0.3 to 200 parts by weight, particularly preferably 3 to 100 parts by weight, more preferably 100 parts by weight of the acrylic resin (A). Is 10 to 50 parts by weight, particularly preferably 15 to 25 parts by weight.
If the amount of the polyfunctional isocyanate compound (B) is too large, the pressure-sensitive adhesive layer becomes too hard and the pressure-sensitive adhesive properties tend to be difficult to obtain, and if it is too small, the elastic modulus tends to decrease and the durability tends to decrease. .

The blending amount of the polyfunctional thiol (C) is preferably 0.5 to 100 parts by weight, particularly preferably 1.5 to 50 parts by weight, more preferably 100 parts by weight of the acrylic resin (A). Is 5 to 25 parts by weight, particularly preferably 7 to 13 parts by weight.
When the blending amount of the polyfunctional thiol is too large, the adhesive property tends to be difficult to be obtained, and when it is too small, the elastic modulus tends to decrease and the durability tends to decrease.

  The content ratio (weight ratio) of the acrylic resin (A), the reaction product of the polyfunctional isocyanate compound (B) and the polyfunctional thiol (C) is 100% by weight of the acrylic resin. The reaction product of the compound (B) and the polyfunctional thiol (C) is preferably 1 to 300 parts by weight, particularly preferably 5 to 150 parts by weight, more preferably 15 to 75 parts by weight, particularly preferably 20 to 20 parts by weight. 40 parts by weight.

  Here, the acrylic pressure-sensitive adhesive of the present invention has a structure in which the acrylic resin (A) is crosslinked with a reaction product of the polyfunctional isocyanate compound (B) and the polyfunctional thiol (C). In the acrylic pressure-sensitive adhesive, a reaction product of the acrylic resin (A) and the polyfunctional isocyanate compound (B), a reaction product of the acrylic resin (A) and the polyfunctional thiol (C), a polyfunctional product A reaction product of the isocyanate compound (B) and the polyfunctional thiol (C) may be contained.

  Moreover, in order to make the acrylic adhesive of this invention suitable as an adhesive for optical members, the adhesiveness with respect to an optical member improves that it further contains a silane coupling agent (D). This is preferable.

  Examples of the silane coupling agent (D) include an epoxy group-containing silane coupling agent, a (meth) acryloyl group-containing silane coupling agent, a mercapto group-containing silane coupling agent, a hydroxyl group-containing silane coupling agent, and a carboxyl group-containing. Examples thereof include a silane coupling agent, an amino group-containing silane coupling agent, an amide group-containing silane coupling agent, and an isocyanate group-containing silane coupling agent. These may be used alone or in combination of two or more. Among these, an epoxy group-containing silane coupling agent is preferably used.

  Specific examples of the epoxy group-containing silane coupling agent include γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, and γ-glycol. Sidoxypropylmethyldimethoxysilane, methyltri (glycidyl) silane, β- (3,4 epoxycyclohexyl) ethyltrimethoxysilane, β- (3,4epoxycyclohexyl) ethyltrimethoxysilane, epoxy group-containing silicone alkoxy oligomer (epoxy group) Modified ethyl / methyl silicate low condensate), etc., among which γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, β- 3,4-epoxycyclohexyl) ethyltrimethoxysilane, epoxy group-containing silicone alkoxy oligomer (an epoxy group-modified ethyl / methyl silicate low condensate).

  Specific examples of the mercapto group-containing silane coupling agent include, for example, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, γ-mercaptopropyldimethoxymethylsilane, SH group-containing silicone alkoxy oligomer (mercapto group-modified). Ethyl / methyl silicate low condensate).

The content of the silane coupling agent (D) is preferably 0.01 to 10 parts by weight, particularly preferably 0.02 to 1 part by weight, based on 100 parts by weight of the acrylic resin (A). Preferably it is 0.03-0.5 weight part.
If the content of the silane coupling agent (D) is too small, there is a tendency that the addition effect cannot be obtained. If the content is too large, the compatibility with the acrylic resin (A) is lowered and adhesive strength and cohesive strength are obtained. There is a tendency to disappear.

  In addition, the acrylic pressure-sensitive adhesive of the present invention further includes an antistatic agent, other acrylic pressure-sensitive adhesives, other pressure-sensitive adhesives, urethane resin, rosin, rosin ester, and hydrogenated rosin as long as the effects of the present invention are not impaired. UV absorption of tackifiers such as esters, phenol resins, aromatic modified terpene resins, aliphatic petroleum resins, alicyclic petroleum resins, styrene resins, xylene resins, colorants, fillers, and anti-aging agents Conventionally known additives such as agents and functional dyes, and compounds that cause coloration or discoloration upon irradiation with ultraviolet rays or radiation can be blended. In addition to the above additives, a small amount of impurities contained in the raw materials for producing the constituent components of the pressure-sensitive adhesive composition may be contained.

  The antistatic agent preferably contains an alkali metal salt or a nitrogen-containing organic cation.

  In general, an ene-thiol reaction by mixing a polyfunctional acrylate compound and a polyfunctional thiol compound and irradiating with UV is known. In the present invention, the polyfunctional thiol compound (C) exhibits the effects of the present invention by reacting with the polyfunctional isocyanate compound (B) instead of the polyfunctional acrylate. Therefore, the pressure-sensitive adhesive composition of the present invention preferably does not contain a polyfunctional acrylate compound, but may be contained to the extent that the effects of the present invention are not impaired. The content is usually 10% or less, preferably 5% or less, more preferably 1% or less.

When the acrylic pressure-sensitive adhesive of the present invention is used for applications that require corrosion resistance, such as transparent electrode films such as ITO film and ITO glass, and meshes such as electromagnetic wave shields, the acrylic pressure-sensitive adhesive is substantially It is preferable that no acidic group is contained.
“Substantially no acidic group” means that no monomer having an acidic group is used as a copolymerization component of the acrylic resin (A), and the acid value of the entire pressure-sensitive adhesive composition is preferably 10 mgKOH / g or less, particularly preferably. Means 1 mgKOH / g or less.

  Next, the manufacturing method of the acrylic adhesive of this invention is demonstrated.

  The acrylic pressure-sensitive adhesive of the present invention can be produced by various methods as long as the acrylic resin (A) is crosslinked with a reaction product of the polyfunctional isocyanate compound (B) and the polyfunctional thiol (C). However, a method of reacting the polyfunctional isocyanate compound (B) with the polyfunctional thiol (C) in the presence of the acrylic resin (A) is preferable in terms of excellent durability. .

  Specifically, an acrylic pressure-sensitive adhesive composition containing an acrylic resin (A), a polyfunctional isocyanate compound (B), and a polyfunctional thiol (C) is coated on a substrate, dried, and aged. The method of manufacturing by doing is preferable.

  When coating the acrylic pressure-sensitive adhesive, it is preferable to dilute the pressure-sensitive adhesive composition in a solvent, and the dilution concentration is preferably 5 to 80% by weight, particularly preferably 10 to 50% by weight. Especially preferred is 15 to 30% by weight. The solvent is not particularly limited as long as it dissolves the acrylic pressure-sensitive adhesive. For example, ester solvents such as methyl acetate, ethyl acetate, methyl acetoacetate and ethyl acetoacetate, acetone, methyl ethyl ketone, A ketone solvent such as methyl isobutyl ketone, an aromatic solvent such as toluene and xylene, and an alcohol solvent such as methanol, ethanol and propyl alcohol can be used. Among these, ethyl acetate and methyl ethyl ketone are preferably used from the viewpoints of solubility, drying property, price, and the like.

  The drying conditions are usually 60 to 130 ° C. (preferably 70 ° C. to 110 ° C.) and usually 5 seconds to 30 minutes (preferably 30 seconds to 3 minutes).

  The aging treatment is carried out to balance the physical properties of the adhesive. As aging conditions, the temperature is usually from room temperature to 70 ° C., and the time is usually from 1 day to 30 days. What is necessary is just to carry out on conditions, such as 1 day-30 days at 23 degreeC, 3-10 days at 23 degreeC, 1 day-7 days at 40 degreeC.

  The pressure-sensitive adhesive composition can be applied by a conventional method such as roll coating, die coating, gravure coating, comma coating, or screen printing.

  In addition, when using the acrylic adhesive of this invention as an adhesive for optical members, what is necessary is just to use an optical member (optical laminated body) as said base material, and the adhesive layer which consists of this adhesive for optical members is used. By laminating and forming on an optical member (for example, an optical laminate), an optical member with an adhesive layer can be obtained.

  The optical member with the pressure-sensitive adhesive layer is preferably provided with a release sheet on the surface opposite to the optical member surface of the pressure-sensitive adhesive layer, and when the optical member with the pressure-sensitive adhesive layer is practically used, The release sheet is peeled off and used. And as said release sheet, it is preferable to use a silicon-type release sheet.

  In preparing the optical member with the pressure-sensitive adhesive layer, for the method of crosslinking the pressure-sensitive adhesive composition for the optical member, [1] on the optical member, after applying and drying the pressure-sensitive adhesive composition for the optical member, A method of pasting a release sheet and performing an aging treatment, [2] A method of applying an adhesive composition for an optical member on a release sheet, drying, pasting an optical member, and performing an aging treatment Can be done. Among these, the method [2] is preferable from the viewpoint of not damaging the substrate, workability and stable production.

  Moreover, 5-300 micrometers is preferable normally, and, as for the thickness of the adhesive layer in the optical member with an adhesive layer obtained, 5-50 micrometers is especially preferable, Furthermore, 10-30 micrometers is preferable. If the thickness of the pressure-sensitive adhesive layer is too thin, the adhesive physical properties tend to be difficult to stabilize, and if it is too thick, the entire optical member tends to be too thick.

  The optical member with the pressure-sensitive adhesive layer of the present invention has a release sheet, and after the release sheet is peeled off, the pressure-sensitive adhesive layer surface is bonded to a glass substrate and used for, for example, a liquid crystal display device.

  The optical member in the present invention is not particularly limited, and an optical film suitably used for an image display device such as a liquid crystal display device, an organic EL display device, or a PDP, such as a polarizing plate, a retardation plate, or an elliptical polarizing plate. , Optical compensation films, brightness enhancement films, and those in which these are laminated. Among them, a polarizing plate is particularly effective in the present invention.

  The polarizing plate used in the present invention is usually a laminate of a cellulose triacetate film as a protective film on both sides of a polarizing film. The polarizing film has an average degree of polymerization of 1,500 to 10,000, A uniaxially stretched film dyed with an aqueous solution of iodine-potassium iodide or a dichroic dye using a film made of a polyvinyl alcohol resin having a degree of conversion of 85 to 100 mol% as a raw film (usually 2 to 10 times, preferably Is a stretching ratio of about 3 to 7 times.

  The polyvinyl alcohol resin is usually produced by saponifying polyvinyl acetate obtained by polymerizing vinyl acetate, but a small amount of unsaturated carboxylic acid (including salt, ester, amide, nitrile, etc.), olefins, vinyl ether And a component copolymerizable with vinyl acetate, such as an unsaturated sulfonate. Moreover, what is called polyvinyl acetal resin and polyvinyl alcohol derivatives, such as polybutyral resin and polyvinyl formal resin, which are obtained by reacting polyvinyl alcohol with an aldehyde in the presence of an acid are also exemplified.

  The pressure-sensitive adhesive of the present invention includes various displays such as word processors, computers, mobile phones, and televisions, optical parts such as polarizing plates and laminates corresponding thereto, pressure-sensitive adhesives for temporary surface protection of electronic substrates, and pressure-sensitive adhesives for double-sided tapes. It can also be used as medical adhesives, surface protective adhesives, general label adhesives, toy seal adhesives, decorative seal adhesives, and uneven follow-up adhesives.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist. In the examples, “parts” and “%” mean weight basis.

First, various acrylic resins were prepared as follows. In addition, regarding the measurement of the weight average molecular weight of acrylic resin, dispersion degree, and glass transition temperature, it measured according to the above-mentioned method.
In addition, regarding the measurement of a viscosity, it measured according to the 4.5.3 rotational viscometer method of JISK5400 (1990).

[Preparation of Acrylic Resin (A)] (See Table 1)
[Acrylic resin (A-1)]
In a four-necked round bottom flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet and a thermometer, 5 parts of acrylic acid (a2), 95 parts of butyl acrylate (a1), 100 parts of ethyl acetate, acetone 45 After starting to reflux with heating, 0.03 part of azobisisobutyronitrile (AIBN) was added as a polymerization initiator, reacted for 3 hours at the reflux temperature of ethyl acetate, diluted with ethyl acetate, and acrylic resin ( A-1) A solution (weight average molecular weight (Mw) 1,520,000, dispersity (Mw / Mn) 3.4, glass transition temperature -51 ° C., solid content 23%, viscosity 8,000 mPa · s (25 ° C.)) Obtained.

[Acrylic resin (A-2)]
In a four-necked round bottom flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet and a thermometer, 5 parts of acrylic acid (a2), 75 parts of butyl acrylate (a1), and phenoxyethyl acrylate (a3) 20 Parts, 100 parts of ethyl acetate and 45 parts of acetone. After heating to reflux, 0.03 part of azobisisobutyronitrile (AIBN) was added as a polymerization initiator, and the mixture was reacted at ethyl acetate reflux temperature for 3 hours. Acrylic resin (A-2) solution (weight average molecular weight (Mw) 150,000, dispersion degree (Mw / Mn) 3.5, glass transition temperature -45 ° C, solid content 22%, viscosity 8, 000 mPa · s (25 ° C.)).

[Example 1]
To 100 parts of acrylic resin (A-1), 20 parts of polyfunctional isocyanate compound (B-1) (trimethylolpropane adduct of tolylene diisocyanate; manufactured by Nippon Polyurethane Co., Ltd .; trade name “Coronate L”), polyfunctional 10.6 parts of thiol (C-1) (trimethylolpropane tris (3-mercaptopropionate); manufactured by SC Organic Chemicals; trade name “TMMP”) was blended to prepare an acrylic pressure-sensitive adhesive composition.

[Example 2]
To 100 parts of acrylic resin (A-2), polyfunctional isocyanate compound (B-1) (trimethylolpropane adduct of tolylene diisocyanate, trimethylolpropane adduct of tolylene diisocyanate; manufactured by Nippon Polyurethane Co., Ltd .; Coronate L ") 20 parts, polyfunctional thiol (C-1) (trimethylolpropane tris (3-mercaptopropionate); SC Organic Chemical Co., Ltd .; trade name" TMMP ") 10.6 parts, and acrylic A pressure-sensitive adhesive composition was prepared.

Example 3
To 100 parts of acrylic resin (A-1), polyfunctional isocyanate compound (B-1) (trimethylolpropane adduct of tolylene diisocyanate, trimethylolpropane adduct of tolylene diisocyanate; manufactured by Nippon Polyurethane Co., Ltd .; 20 parts of coronate L "), polyfunctional thiol (C-2) (pentaerythritol tetrakis (3-mercaptopropionate)); manufactured by SC Organic Chemical Co., Ltd .; trade name" PEMP ") 9.8 parts, and acrylic A pressure-sensitive adhesive composition was prepared.

[Comparative Example 1]
An acrylic pressure-sensitive adhesive composition solution was prepared in the same manner as in Example 1 except that the polyfunctional thiol (C-1) was not blended in Example 1.

[Comparative Example 2]
In Example 1, the acrylic adhesive was changed in the same manner as in Example 1 except that the amount of the polyfunctional isocyanate compound (B-1) was changed to 8 parts and the polyfunctional thiol (C-1) was not added. An agent composition solution was prepared.

[Comparative Example 3]
In Example 1, the amount of the polyfunctional isocyanate compound (B-1) was changed to 1.5 parts, and the acrylic was treated in the same manner as in Example 1 except that the polyfunctional thiol (C-1) was not blended. A system pressure-sensitive adhesive composition solution was prepared.

[Preparation of PET film with adhesive layer]
The pressure-sensitive adhesive composition solutions of Examples 1 to 3 and Comparative Examples 1 to 3 were applied to a polyester release sheet so that the thickness after drying was 25 μm, dried at 90 ° C. for 3 minutes, and then formed. The pressure-sensitive adhesive composition layer side was transferred onto a polyethylene terephthalate (PET) film (thickness 38 μm), and then 23 ° C. × 65% R.D. H. The film was aged for 10 days under the above conditions to obtain a PET film with an adhesive layer.

  Using the PET film with the pressure-sensitive adhesive layer obtained in this manner, the gel fraction was measured and evaluated according to the following methods for the following items. These results are also shown in Table 1 below.

[Gel fraction]
After the obtained PET film with the pressure-sensitive adhesive layer is cut into 40 × 40 mm, the release sheet is peeled off and the pressure-sensitive adhesive layer side is bonded to a 50 × 100 mm SUS mesh sheet (200 mesh), and then the SUS mesh sheet. The sample was wrapped from the center with respect to the longitudinal direction, and the sample was wrapped. Then, the gel fraction was measured by weight change when immersed in a sealed container containing 250 g of toluene.

[Preparation of polarizing plate with adhesive layer]
The pressure-sensitive adhesive composition solutions of Examples 1 to 3 and Comparative Examples 1 to 3 were applied to a polyester release sheet so that the thickness after drying was 25 μm, dried at 90 ° C. for 3 minutes, and then formed. The pressure-sensitive adhesive composition layer was transferred onto a polarizing plate (thickness 190 μm), and then 23 ° C. × 65% R.D. H. The film was aged for 10 days under the above conditions to obtain a polarizing plate with an adhesive layer.
For the polarizing plate, “MLP38U” manufactured by Biei Imaging Co., Ltd. was used by cutting it at 45 ° C. with respect to the stretching axis.

  Using the polarizing plate with the pressure-sensitive adhesive layer thus obtained, durability (wet heat resistance test, heat cycle test, heat resistance test) and adhesive strength were measured and evaluated according to the following methods. These results are also shown in Table 2 below.

〔durability〕
The release sheet of the obtained polarizing plate with the pressure-sensitive adhesive layer was peeled off, and the pressure-sensitive adhesive layer side was pressed against a non-alkali glass plate (Corning Corp., Eagle XG) to bond the polarizing plate and the glass plate. Thereafter, autoclave treatment (50 ° C., 0.5 MPa, 20 minutes) was performed, and thereafter, peeling and foaming were evaluated in the following durability tests (1) to (3) (moisture and heat resistance test, heat resistance test).
Furthermore, in the heat resistance test of (3) below, in addition to the evaluation of foaming and peeling, a sample for light leakage observation was prepared by bonding the same sample on both the front and back so that the polarizing plate became crossed Nicol. The light leakage phenomenon was also evaluated.
The test piece size used was 20 cm × 15 cm.

〔An endurance test〕
(1) Moisture and heat resistance test 60 ° C., 90% R.D. H. Endurance test for 150 hours (2) Thermal shock test -30 ° C and 70 ° C for 30 min cycle 150 hours (3) Heat test 80 ° C for 150 hours endurance test and light leakage

〔Evaluation criteria〕
(Peeling)
○: Peeling less than 0.5 mm or occurrence of a lift mark Δ ... Peeling of 0.5 mm or more and less than 10 mm, or generation of a lift mark × ... Peeling of 10 mm or more, or a lift mark of 10 mm or more Occurrence (foaming)
○: Foam is hardly seen △ ... Foam is slightly seen × ... Foam is seen a lot (light leakage)
◎ ・ ・ ・ Light leakage is excellent ○ ・ ・ ・ Light leakage is hardly seen △ ・ ・ ・ Light leakage is slightly generated × ・ ・ ・ Light leakage is large on 4 sides

[Adhesive force]
About a polarizing plate with an adhesive layer, it cut | judged to width 25mm width, peels a release film, presses the adhesive layer side to a non-alkali glass plate (Corning company make, "Corning 1737"), and a polarizing plate A glass plate was bonded. Then, after performing an autoclave process (50 degreeC, 0.5 MPa, 20 minutes), 23 degreeC and 50% R. H. The adhesive strength after standing for 7 days was measured by a 180 ° C. peel test, and the adhesive strength (2) was further increased to 40 ° C. and 50% R.D. H. The adhesive strength after standing for 7 days was measured by a 180 ° C. peel test.

[Production of alkali-free glass plate with adhesive layer]
After apply | coating the adhesive composition solution of the said Examples 1-3 and Comparative Examples 1-3 to a light release polyester type | mold release sheet so that the thickness after drying may be 25 micrometers, and drying for 3 minutes at 90 degreeC. The formed pressure-sensitive adhesive composition layer side was transferred onto a heavy release polyester release sheet, and then 23 ° C. × 65% R.D. H. The substrate-less double-sided PSA sheet was obtained by aging for 10 days under the above conditions.
The substrate-less double-sided pressure-sensitive adhesive sheet is cut out to 3 cm × 4 cm, the light release release sheet is peeled off, the pressure-sensitive adhesive layer side is pressed against a non-alkali glass plate (Corning Corp. Eagle XG), and further heavy release release is performed. The mold sheet was peeled off to obtain an alkali-free glass plate with an adhesive layer.

[Haze]
The diffuse transmittance and total light transmittance of the alkali-free glass plate with the pressure-sensitive adhesive layer were measured using HAZE MATER NDH2000 (manufactured by Nippon Denshoku Industries Co., Ltd.). This machine complies with JIS K7361-1.
The values of the obtained diffuse transmittance and total light transmittance were substituted into the following formula to calculate haze.
Haze (%) = (diffuse transmittance / total light transmittance) × 100

※）表中（ ）内の数字は重量部を表す。

*) Numbers in parentheses in the table represent parts by weight.

  The acrylic pressure-sensitive adhesive obtained from the acrylic resin (A), the polyfunctional isocyanate compound (B) and the polyfunctional thiol (C) in Examples 1 to 3 is excellent in durability, light leakage, and transparency. It can be seen that the adhesive is stable (the difference in adhesive strength (1) and (2) is within 20%) within about one week.

On the other hand, the acrylic pressure-sensitive adhesive of Comparative Example 3 containing no polyfunctional thiol (C) and using the polyfunctional isocyanate compound (B) in a blending amount as a general crosslinking agent is excellent in durability and transparency. Aging was also stable in about one week, but the light leakage resistance was poor.
In addition, the acrylic pressure-sensitive adhesives of Comparative Examples 1 and 2, which do not contain the polyfunctional thiol (C) and use the polyfunctional isocyanate compound (B) in a larger amount than a general crosslinking agent, are resistant to light leakage. Although it was excellent, it was inferior in durability. Furthermore, since it takes time to react with a large amount of isocyanate groups, it was confirmed that aging was not completed in one week, and that when the aging was further added, the adhesive strength was significantly reduced (crosslinking progressed).

[Comparative Example 4]
Further, as Comparative Example 4, an acrylic pressure-sensitive adhesive composition solution was prepared in the same manner as in Example 1 except that 3.6 parts of trimethylolpropane was blended in place of the polyfunctional thiol (C-1). Produced.
In Comparative Example 4, a polyfunctional alcohol that can be generally reacted with a polyisocyanate is blended. However, since the compatibility is very poor, the obtained adhesive composition solution has haze in the same manner as described above. When measured, the haze value was 24, which was inferior in transparency, and could not be used as an adhesive for optical members.

  The acrylic pressure-sensitive adhesive of the present invention is excellent in durability (particularly durability under severe wet heat conditions) and has excellent optical properties such as light leakage resistance and transparency and reworkability. It is useful as an adhesive, and is very useful as an adhesive for obtaining an optical member with an adhesive layer and an image display device obtained by using them.

Claims (10)

  An acrylic pressure-sensitive adhesive obtained by crosslinking an acrylic resin (A) with a reaction product of a polyfunctional isocyanate compound (B) and a polyfunctional thiol (C).   The acrylic adhesive according to claim 1, wherein the polyfunctional isocyanate compound (B) is a tolylene diisocyanate compound.   The acrylic pressure-sensitive adhesive according to claim 1 or 2, wherein the polyfunctional thiol (C) has a thiol group content of 2 to 10.   The content of the reaction product of the polyfunctional isocyanate compound (B) and the polyfunctional thiol (C) is 5 to 100 parts by weight with respect to 100 parts by weight of the acrylic resin (A). The acrylic adhesive in any one of 1-3.   A pressure-sensitive adhesive for optical members, comprising the acrylic pressure-sensitive adhesive according to claim 1.   6. The optical member pressure-sensitive adhesive according to claim 5, wherein the optical member is a polarizing plate.   The optical member with an adhesive layer containing the laminated structure of the adhesive layer containing the adhesive for optical members of Claim 5 or 6, and an optical member.   An image display device comprising the optical member with an adhesive layer according to claim 7.   The acrylic composition according to any one of claims 1 to 4, wherein a pressure-sensitive adhesive composition containing an acrylic resin (A), a polyfunctional isocyanate compound (B), and a polyfunctional thiol (C) is coated and dried. Method for producing a pressure-sensitive adhesive.   An acrylic pressure-sensitive adhesive composition comprising an acrylic resin (A), a polyfunctional isocyanate compound (B), and a polyfunctional thiol (C).